Information available at the present time indicates a relationship between nutritional factors and idiopathic bladder stone disease. Studies in Thailand indicate that the several factors involved include: (a) low dietary phosphate intake leading to low urinary phosphate excretion; (b) high urinary oxalate excretion resulting from both high oxalate consumption and possibly high endogenous oxalate production, (c) low excretion of substances that enhance solubility or inhibit crystallization; (d) dehydration resulting from hot climate, diarrhea, vomiting, and febrile illnesses; (e) other unknown factors. These factors lead to heavy oxalate crystalluria, crystal clumping, and nidus formation. However, oral orthophosphate supplementations could eliminate oxalate crystalluria and clumping within 48 hours. At the same time, a marked increase of urinary total phosphate and pyrophosphate (twofold to tenfold) and significant decreases in urinary oxalate and calcium excretion were observed during the phosphate supplementation. It is thought that crystalluria, particularly oxalate, is a forerunner of bladder stone disease. Therefore, dietary phosphate that can prevent or eliminate crystalluria may provide a means for the prevention of bladder stone disease. The trial preventive program in Thailand started in 1974 were to test the effectiveness of oral inorganic phosphate supplementation in: (a) protection against oxalcrystalluria; (b) prevention of the occurrence of presumptive stone symptoms; and (c) reduction in the incidence of bladder stone disease.